Datenblatt für AL5801 von Diodes Incorporated

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AL5801
Document number: DS35555 Rev. 3 - 2
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L5801
100V, ADJUSTABLE CURRENT SINK LINEAR LED DRIVER
Description
The AL5801 combines a 100V N-channel MOSFET with a pre-
biased NPN transistor to make a simple, small footprint LED driver.
The LED current is set by an external resistor connected from REXT
pin (4) to GND pin (6). The internal pre-biased transistor develops
approximately 0.56V across the external resistor.
The AL5801 open-drain output can operate from 1.1V to 100V
enabling it to operate 5V to 100V power supplies without additional
components.
PWM dimming of the LED current can be achieved by driving the
BIAS pin (1) with an external, open-collector NPN transistor or
open-drain N-channel MOSFET.
The AL5801 is available in a SOT26 package and is ideal for driving
LED currents up to 350mA.
Features
• Feedback Pin Reference Voltage VRSET = 0.56V at +25°C
• -40°C to +125°C Temperature Range
• 1.1V to 100V Open-Drain Output
• Negative temperature VRSET co-efficient automatically reduces
the LED current at high temperatures
• Low thermal impedance SOT26 package with copper lead
frame
• Lead-Free Finish; RoHS Compliant (Notes 1 & 2)
• Halogen and Antimony Free. “Green” Device (Note 3)
• Qualified to AEC-Q101 Standards for High Reliability
Pin Assignments
(Top View)
SOT26
Applications
• Linear LED Drivers
• LED Signs
• Offline LED Luminaries
Notes: 1. EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. All applicable RoHS exemptions applied.
2. See http://www.diodes.com for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green" and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl)
and <1000ppm antimony compounds.
Typical Applications Circuit
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Pin Descriptions
Pin
Number Pin
Name Function
1 BIAS Biases the open-Drain output MOSFET
2 FB Feedback pin
3 OUT Open-Drain LED driver output
4 REXT Current sense pin. LED current sensing resistor should be connected from here to GND
5 COMP
Compensation pin. Connect COMP pin to REXT pin and insert a 1nF ceramic capacitor from COMP
pin to FB pin for improved transient stability
6 GND Ground reference point for setting the LED current
Functional Block Diagram
Figure 1 Block Diagram
Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.)
Symbol Characteristics Values Unit
VOUT Output voltage relative to GND 100 V
VBIAS BIAS voltage relative to GND (Note 4) 20 V
VFB FB voltage relative to GND 6 V
VCOMP COMP voltage relative to GND 6 V
VREXT REXT voltage relative to GND 6 V
IOUT Output current 350 mA
TJ Operating junction temperature -40 to +150 °C
TST Storage temperature -55 to +150 °C
Note: 4. With pins 5 and 6 connected together.
These are stress ratings only. Operation outside the absolute maximum ratings may cause device failure.
Operation at the absolute maximum rating for extended periods may reduce device reliability.
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Package Thermal Data
Characteristic Symbol Value Unit
Power Dissipation (Note 5) @ TA = +25°C
PD
0.75
W
Power Dissipation (Note 6) @ TA = +25°C 0.70
Power Dissipation (Note 7) @ TA = +25°C 0.85
Power Dissipation (Note 8) @ TA = +25°C 1.05
Thermal Resistance, Junction to Ambient Air (Note 5) @ TA = +25°C
RθJA
165
°C/W
Thermal Resistance, Junction to Ambient Air (Note 6) @ TA = +25°C 180
Thermal Resistance, Junction to Ambient Air (Note 7) @ TA = +25°C 145
Thermal Resistance, Junction to Ambient Air (Note 8) @ TA = +25°C 120
Notes: 5. Device mounted on 15mm x 15mm 2oz copper board.
6. Device mounted on 25mm x 25mm 1oz copper board.
7. Device mounted on 25mm x 25mm 2oz copper board.
8. Device mounted on 50mm x 50mm 2oz copper board.
Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.)
Symbol Parameter Min Max Unit
VBIAS Supply voltage range 3.5 20 V
VOUT OUT voltage range 1.1 100
ILED LED pin current (Note 9) 25 350 mA
TA Operating ambient temperature range -40 125 °C
Note: 9. Subject to ambient temperature, power dissipation and PCB.
NMOSFET Electrical Characteristics: (Q1) (@TA = +25°C, unless otherwise specified.)
Characteristic Symbol Min Typ Max Unit Test Condition
OFF CHARACTERISTICS
Drain-Source Breakdown Voltage BVDSS 100 ⎯ ⎯ V VGS = 0V, ID = 250µA
Zero Gate Voltage Drain Current IDSS ⎯ ⎯ 1 µA
VDS = 60V, VGS = 0V
Gate-Source Leakage IGSS ⎯ ⎯ ±100 nA VGS = ±20V, VDS = 0V
ON CHARACTERISTICS
Gate Threshold Voltage VGS(th) 2.0 ⎯ 4.1 V
VDS = VGS, ID = 250µA
Static Drain-Source On-Resistance RDS (ON) ⎯ ⎯
⎯
0.85
0.99 Ω VGS = 10V, ID = 1.5A
VGS = 6V, ID = 1A
Forward Transconductance gfs ⎯ 0.9 ⎯ S VDS = 15V, ID = 1A
Diode Forward Voltage VSD ⎯ 0.89 1.1 V
VGS = 0V, IS = 1.5A
DYNAMIC CHARACTERISTICS
Input Capacitance Ciss ⎯ 129 ⎯ pF VDS = 50V, VGS = 0V
f = 1.0MHz
Output Capacitance Coss ⎯ 14 ⎯ pF
Reverse Transfer Capacitance Crss ⎯ 8 ⎯ pF
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Pre-Bias Transistor Electrical Characteristics: (Q2) (@TA = +25°C, unless otherwise specified.)
Characteristic (Note 10) Symbol Min Typ Max Unit Test Condition
Input Voltage VI(off) 0.4 - - V
VCC = 5V, IO = 100μA
VI(on) - - 1.5 V
VCC = 0.3V, IO = 5mA
Output Voltage VO(on) - 0.05 0.3 V
IO/II = 5mA/0.25mA
Output Current IO(off) - - 0.5
μA VCC = 50V, VI = 0V
DC Current Gain G1 80 - - -
VO = 5V, IO = 10mA
Input Resistance R1 3.2 4.7 6.2 kΩ -
Resistance Ratio R2/R1 8 10 12 - -
Notes: 10. Short duration pulse test used to minimize self-heating effect.
Thermal Characteristics
0.2
0.4
0.6
0.8
1.2
0 25 50 75 100 125 150
TEMPERATURE (°C)
Figure 2 Derating Curve
M
A
X
P
O
WE
R
D
ISSI
P
A
T
I
O
N
(W)
1.0
0
50mm x 50mm
(2oz. FR4)
25mm x 25mm
(2oz. FR4)
15mm x 15mm
(2oz. FR4)
0.2
0.4
0.6
0.8
1.2
0 500 1,000 1,500 2,000 2,500
COPPER AREA (mm )
Figure 3 Area vs. Max Power
2
M
AX
P
O
WE
R
D
ISSI
P
A
T
I
O
N
(W)
T = 25°C
2oz. FR4
A
1.0
0
100
120
140
160
180
0.0001 0.001 0.01 0.1 1 10 100 1,000
PULSE WIDTH (s)
Figure 4 Transient Thermal Impedance
J
U
N
C
T
I
O
N
T
O
AMBIE
N
T
AI
R
THERMAL RESISTANCE (°C/W)
T = 25°C
25mm x 25mm
1oz. FR4
A
80
60
40
20
0
D = 0.05
D = 0.1
Single Pulse
D = 0.2
D = 0.5
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Typical Performance Characteristics
0.05
0.15
0.25
0.35
0123
V (V)
OUT
Figure 5 Output Current vs. V
OUT
I (A)
OUT
0
0.10
0.20
0.30
0.40
I = 0.1mA
bias
R = 1.6
EXT
Ω
R = 3.75
EXT
Ω
R = 11.6
EXT
Ω
R = 22.7
EXT
Ω
100
150
200
250
300
350
400
110100
R ()
EXT
Ω
Figure 6 Output Current vs. R
EXT
I (mA)
OUT
50
0
I = 0.1mA
bias
0.1
0.2
0.3
0.4
0.5
01 23
V (V)
OUT
Figure 7 Output Current vs. V
OUT
I (A)
OUT
0
I = 0.1mA
R = 1.6
bias
EXT
Ω
T = -40C
A
°
T = 25C
A
°
T = 85C
A
°
0.05
0.15
02 4 6 810
V (V)
OUT
Figure 8 Output Current vs. V
OUT
0
0.10
0.20
I (A)
OUT
I = 0.1mA
R = 3.75
bias
EXT
Ω
T = -40C
A
°
T = 25C
A
°
T = 85C
A
°
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0 5 10 15
V (V)
OUT
Figure 9 Output Current vs. V
OUT
0
I (A)
OUT
I = 0.1mA
R = 11.6
bias
EXT
Ω
T = -40C
A
°
T = 25C
A
°
T = 85C
A
°
0.005
0.015
0.025
0.035
0 5 10 15 20
V (V)
OUT
Figure 10 Output Current vs. V
OUT
0
0.010
0.020
0.030
I (A)
OUT
I = 0.1mA
R = 22.7
bias
EXT
Ω
T = -40C
A
°
T = 25C
A
°
T = 85C
A
°
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L5801
Typical Performance Characteristics (cont.)
100
200
300
400
500
600
700
800
-50 0 50 100 150
JUNCTION TEMPERATURE ( C)
°
Figure 11 V vs. Junction Temperature
REXT
V (mV)
REXT
I = 0.1mA
V
bias
bias
= 5V
0
0
50
100
150
200
250
300
350
400
110100
V (V)
OUT
Figure 12 Output Current vs. V
OUT
I (mA)
OUT
I = 0.1mA
T = 85°C
bias
A
50mm x 50mm
(2oz. FR4)
25mm x 25mm
(2oz. FR4)
15mm x 15mm
(2oz. FR4)
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AL5801
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L5801
Application Information
Figure 13 Typical Application Circuit for
Linear Mode Current Sink LED Driver
The AL5801 is designed for driving high brightness LEDs with typical LED current up to 350mA. It provides a more cost effective way for driving
low current LEDs when compared against more complex switching regulator solutions. Furthermore, it reduces the PCB board area of the
solution because there is no need for external components like inductors, capacitors and/or switching diodes.
Figure 13 shows a typical application circuit diagram for driving an LED or a string of LEDs. The NPN transistor Q2 measures the LED current by
sensing the voltage across an external resistor REXT. Q2 uses its VBE as reference to set the voltage across REXT and controls the gate voltage of
MOSFET Q1. Q1 operates in linear mode to regulate the LED current. The LED current is:
ILED = VRSET / REXT
where VRSET is the VBE of Q2. VBE is 0.56V typical at a +25°C device temperature. See Figure 11 for the variation of VBE with Q2’s junction
temperature at IBIAS = 0.1mA. VBE has a negative temperature coefficient which reduces the LED current as the device warms up, protecting the
LED(s).
RBIAS should be chosen to drive 0.1mA current into the BIAS pin
RBIAS = ( VCC – 3.75V ) / 0.1mA
From the above equation, for any required LED current the necessary external resistor REXT can be calculated from
REXT = VRSET / ILED
The expected linear mode power dissipation must be factored into the design consideration. The power dissipation across the device can be
calculated by taking the maximum supply voltage less the minimum voltage across the LED string.
VDS(Q1) = VCC(max) – VLED(min) – VRSET
PD = VDS(Q1) * ILED
As the output LED current of AL5801 increases so will its power dissipation. The power dissipation will cause the device temperature to rise
above ambient, TA, by an amount determined by the package thermal resistance, RθJA.
Therefore, the power dissipation supported by the device is dependent upon the PCB board material, the copper area and the ambient
temperature. The maximum dissipation the device can handle is given by:
PD = ( TJ(MAX) - TA ) / RθJA
TJ(MAX) = +150°C is the maximum device junction temperature. Refer to the thermal characteristic graphs in Figure 2 to 4 for selecting the
appropriate PCB copper area. Figure 12 shows the current capabilities of the AL5801 at +25°C with different PCB copper area heat sinks.
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Constant LED Current Temperture Compensation
Variation in the junction temperature of Q2 will cause variations in the value of controlled LED current ILED. The base-emitter VBE voltage of Q2
decreases with increasing temperature at a rate of approximately 2mV/°C. Figure 14 shows a simple temperature compensation network, which
comprises of an NTC thermistor and resistor Rbase, for stabilizing the LED current.
Figure 14 Constant LED Current Temperature Compensation for AL5801
The voltage drop VRSET in the sense resistor REXT should be set to be 40 to 100mV higher than the VBE(Q2) at 25ºC. Figure 11 shows the typical
VBE(Q2) is 0.56V at room temperature with 0.1mA IBIAS, so VRSET is selected to be 0.62V.
With the VRSET chosen, the sense resistor value for 350mA ILED is determined by
REXT = VRSET / ILED = 0.62V / 350mA = 1.77Ω
So a standard resistor value of 1.78Ω with 1% tolerance is used.
The RTH resistance of the NTC thermistor at room temperature is recommended as 10kΩ. The value of base resistor Rbase is set to be 470Ω.
Q2’s base current is obtained as
IB(Q2) = ( VRSET - VBE(Q2) ) / Rbase - VBE(Q2) / RTH = ( 0.62V - 0.56 ) / 470Ω - 0.56V / 10kΩ = 72µA
When VBE(Q2) is changed to VBET as the temperature increases to TºC, the thermistor resistance at T°C required to compensate this variation is
given by
RTHT = VBET / (( VRSET - VBET ) / Rbase - IB(Q2) )
At -2mV/°C, VBE(Q2) reduces to 0.44V from 0.56V as the temperature increases from +25°C to +85°C. From the above equation, the thermistor’s
resistance at +85°C to keep the same output current is given by
RTH85 = 0.44V / (( 0.62V – 0.44V ) / 470Ω - 72µA ) = 1.4kΩ
The NTC thermistor is chosen for compensation whose resistance is 10kΩ at +25°C and 1.38kΩ at +85°C with a β value of 3530.
Figure 15 shows the ILED variation with temperature with and without temperature compensation.
Figure 15 LED Current Variation with and
without Temperature Compensation
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PWM Dimming
(a)
(b)
Figure 16 Application Circuits for LED Driver with PWM Dimming Functionality (a) MOSFET driving and (b) Transistor driving
PWM dimming can be achieved by driving the BIAS pin (1). An external open-collector NPN transistor or open-drain N-channel MOSFET can be
used to drive the BIAS pin as shown in Figure 16. Dimming is achieved by turning the LEDs ON and OFF for a portion of a single cycle. The
PWM signal can be provided by a micro-controller or by analog circuitry.
Figure 17 shows the LED current against the PWM signal duty ratio when the AL5801 is used to drive three series connected LEDs from a 12V
supply. The PWM dimming frequency is set to 200Hz. The PWM signal is supplied to the open-Drain small signal MOSFET’s gate as shown in
Figure 16a. The BIAS pin signal is an inversion of the PWM drive to the MOSFET’s gate. Therefore, a PWM signal duty cycle of 0% provides the
maximum LED current. Sufficiently large PCB copper area is used for heat sinking of the AL5801 in order to minimize the device self-heating at
+25°C ambient.
Figure 17 LED Current against PWM Dimming Signal Duty Ratio at 200Hz PWM Frequency
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Ordering Information
Part Number Qualification Package
Code Packaging
(Note 11)
7” Tape and Reel
Quantity Part Number Suffix
AL5801W6-7 Commercial W6 SOT26 3,000/Tape & Reel -7
AL5801W6Q-7 Automotive W6 SOT26 3,000/Tape & Reel -7
Notes: 11. For packaging details, go to our website at http://www.diodes.com
Marking Information
Date Code Key
Year 2012 2013 2014 2015 2016 2017 2018
Code Z A B C D E F
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Code 1 2 3 4 5 6 7 8 9 O N D
Package Outline Dimensions (All dimensions in mm.)
Suggested Pad Layout
SOT26
Dim Min Max Typ
A 0.35 0.50 0.38
B 1.50 1.70 1.60
C 2.70 3.00 2.80
D ⎯ ⎯ 0.95
H 2.90 3.10 3.00
J 0.013 0.10 0.05
K 1.00 1.30 1.10
L 0.35 0.55 0.40
M 0.10 0.20 0.15
α 0° 8°
⎯
All Dimensions in mm
Dimensions Value (in mm)
Z 3.20
G 1.60
X 0.55
Y 0.80
C1 2.40
C2 0.95
Green
Green
L100 = Product Type Marking Code
YM = Date Code Marking
Y = Year (ex: Y = 2012)
M = Month (ex: 9 = September)
A
M
JL
D
B C
H
K
X
Z
Y
C1
C2
C2
G
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